The Office of Naval Research (ONR], NOAA, and NSF, with the 

 cooperation of other agencies, provide U.S. support for FAMOUS. 

 The project, designed to examine the geological and geophysical 

 processes along the Mid-Atlantic Ridge in the vicinity of the Azores, 

 began in 1971 with a broad regional survey, followed by more 

 intense, localized studies of the valley along the crust of the ridge. 

 This preliminary work provided the basis for an intensive 

 submersible diving program on the ridge during 1974. One U.S. and 

 two French submersibles made 44 dives to the floor of the rift valley 

 and recovered over 1,000 kilograms of rock samples. 



The floor of the rift valley has proved to be much more complex 

 than data collected from the sea surface indicated. The central part of 

 the valley floor has a series of topographic ridges and depressions 

 running along the axis where new sea floor is being created. To either 

 side of this central axial zone, the rift valley has marginal 

 depressions formed by normal faulting along tensional fractures. 

 The faults and fissures show horizontal separations ranging from a 

 few centimeters to over 8 meters. The walls of the rift valley are 

 normal faults along which portions of the old valley floor have been 

 uplifted to form the present crestal ridges. Measured vertical 

 displacements on the faults ranged from less than 1 meter to over 100 

 meters. Although volcanism appeared to be episodic and restricted 

 to the narrow central zone, evidence for continuing tectonic activity 

 was found throughout the dive area. Petrologic and chemical 

 analyses of the recovered basalt show a range of composition similar 

 to that which has been shown for basalts of the Atlantic Ocean as a 

 whole. The most significant variations are in the content of titanium, 

 silica, iron, magnesium, calcium, and potassium. Amounts of some of 

 these elements tend to be low in basalt from the young axial volcanic 

 highs and comparatively high in samples from the rift valley walls. 



Continued analyses of the samples, photographs, and other data 

 from project FAMOUS should significantly improve our understan- 

 ding of the sea-floor accretion process. Future, less elaborate 

 programs using submersibles are now being planned for the 

 Caribbean and eastern equatorial Pacific. These programs will 

 examine the sea-floor spreading process along ridges that differ 

 morphologically and structurally from the Mid-Atlantic Ridge. 



Leg 37 of the Deep Sea Drilling Program (DSDP), supported by 

 NSF, added significant data on the structure and petrology of the 

 Mid-Atlantic Ridge. Although not part of FAMOUS, site 332 was 

 located 25 kilometers west of the FAMOUS dive area and penetrated 

 582 meters into basaltic basement. Preliminary results indicated 

 that the entire section formed within a median valley of Mid-to-Late 

 Pliocene age over a period of 100,000 to 200,000 years. The cored 

 basalt is largely an extrusive sequence of massive to pillowed basalt 



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